I. Field of the Invention
This invention relates to fuel pumping and transfer systems and, in particular, to a fuel transfer system for a multiple shaft gas turbine engine.
II. Background of the Invention
The slinger-type fuel injection system has been utilized in single spool trubine engines for many years. The slinger-type system has proven to have many advantages including low cost, the ability to handle contaminated and slurry fuels and the ability to promote stable combustion at extremely high altitudes where low pressure conditions exist. In the single spool engine, the slinger is part of the main shaft and supplies fuel by introducing the fuel to the interior of the turbine shaft for subsequent injection into the combustion chamber.
Despite the reliability of the slinger-type fuel injection system in single spool engines, similar systems do not provide the same advantages in multiple shaft engines. Most modern turbo-fan or turbo-shaft engines employ multiple shafts wherein a second shaft is internal to the mainshaft. In order to use a slinger-type fuel injection system, the known multiple shaft engines have required a stationary manifold external to the mainshaft of the engine. This manifold is supplied with fuel from tubing which passes through the engine combustion section.
The stationary manifold injects the fuel into a rotating manifold which is attached but external to the mainshaft.
Because of the added structure, the system introduces added costs. Moreover, the ability to handle contaminated slurry or low viscosity fuels is substantially reduced due to the requirement for small orifices in the stationary manifold. Additionally, with either the single shaft or multiple shaft turbine engines, a high pressure fuel pump is required to increase the fuel pressure to combustor entry pressure.